1. Field of the Invention
The present invention generally relates to a structure configured for mounting a holder to an electrical junction box, and in particular to a holder-mounting structure configured for mounting a holder, to which an electric component is attached, on a holder mounting portion provided in an electrical junction box.
2. Description of Related Art
FIG. 10 illustrates a conventional holder-mounting structure 101. The holder-mounting structure 101 is configured for mounting (A) a holder 102 to (B) a holder mounting portion 105 provided in an electrical junction box. In the figure, a dark-current fuse 115 is attached to the holder 102. The dark-current fuse 115 is a known in-between component connected both to a dark-current component and a power source that deliver electrical power to the dark-current component, the dark-current component may comprise a component having a clock function that has to be kept active even when an ignition is turned off.
A known holder-mounting structure of this type is disclosed, for example, in Japanese Patent Application Laid-Open Publication No. H05-159693.
As shown in FIG. 10, the holder 102 comprises (a) a holder body 103 in a shape of a box defined by a top wall 109 and side walls 110 continuing to the peripheral portion of the top wall 109; and (b) a pair of locking wall portions 104 protruding from the side walls 110 in a shape of a plate such that the locking wall portions 104 are spaced from each other and from the top wall 109. The dark-current fuse 115 is attached to the holder body 103.
The pair of locking wall portions 104 each include (i) a provisional-locking portion 111 and (ii) a complete-locking portion 112 closer to a top of the locking wall portion 104 than the provisional-locking portion 111 is. In FIG. 10, the arrow Y represents a direction in which the locking wall portion 104 extend from the top wall 109, and the arrow X represents a direction in which the pair of locking wall portions 104 are arranged.
Still referring to FIG. 10, the holder mounting portion 105 comprises (a) a mounting portion body 106 in a shape of a box defined by a bottom wall and side walls 114; (b) a pair of provisional-locking arms 107 extending from the bottom wall in the direction indicated by the arrow Y and adapted to be elastically deformable in the direction indicated by the arrow X; and (c) a pair of complete-locking arm 108 extending from the bottom wall in the direction indicated by the arrow Y and adapted to be elastically deformable in the direction indicated by the arrow X. The provisional-locking arms 107 and the complete-locking arms 108 are provided such that each of the locking wall portions 104 resides in-between, i.e., sandwiched by the provisional-locking arm 107 and the complete-locking arm 108 in the direction indicated by the arrow X. The provisional-locking arm 107 includes a provisional-locking engagement portion 116 configured to be brought into locking engagement with the provisional-locking portion 111. The complete-locking arm 108 includes a complete-locking engagement portion 117 configured to be brought into locking engagement with the complete-locking portion 112. The locking arms 107, 108 have a uniform thickness from an end continuing to the bottom wall to the other end away from the bottom wall in the direction indicated by the arrow X. Also, the mounting portion body 106 includes a female terminal 118 connected to the power source and circuits of various electronic components.
Operation for mounting the conventional holder 102 to the holder mounting portion 105 can be described as follows. First, the dark-current fuse 115 is attached to the holder body 103. Next, the holder 102 is moved close to the holder mounting portion 105 such that the pair of locking wall portions 104 enter a space between the pair of provisional-locking arms 107 until the provisional-locking engagement portion 116 is brought into locking engagement with the provisional-locking portion 111. In this state of locking engagement, the dark-current fuse 115 and the female terminal 118 are spaced from each other and is electrically disconnected from each other. The holder 102 is further moved close to the holder mounting portion 105 until the complete-locking engagement portion 117 is brought into locking engagement with the complete-locking portion 112. In this manner, when the complete-locking engagement portion 117 is in locking engagement with the complete-locking portion 112, the dark-current fuse 115 and the female terminal 118 are electrically connected to each other.
As the number of electronic devices incorporated in an automobile has been increasing in recent years, electric junction boxes, which incorporates various electric components, need to have spaces for a mechanism of electrical connection and disconnection of the dark-current fuse 115.
To address such a current trend, the thickness of the entire locking arms 107, 108 (in the direction indicated by the arrow X) may be reduced for making the holder mounting portion 105 more low-profile and providing a space for mounting of the electric component. However, uniform reduction in the thickness of the locking arms 107, 108 can cause the locking arms 107, 108 to be bent or broken, which makes it difficult to ensure sufficient mechanical strength of the locking arms 107, 108 that have to reliably hold the holder 102.
In contrast, a uniformly increased thickness of the locking arms 107, 108 to ensure a desired mechanical strength often results in a larger size and dimension of the holder mounting portion 105 (in the direction indicated by the arrow X). In other words, a conventional low-profile or miniaturized holder-mounting structure 101 would fail to ensure mechanical strength of the locking arms 107, 108 needed to hold the holder 102.
In addition, the provisional-locking arms 107 and the complete-locking arms 108 of in the conventional holder-mounting structure 101 are arranged in alignment with each other in the direction indicated by the arrow X. This means that these locking arms 107, 108 are elastically deformed in the same direction (i.e., the direction indicated by the arrow X), which in turn means that the conventional holder-mounting structure 101 becomes further larger in size.